Calculator Problem. Thanks for helping! ^^

[clark_sandy]

greetings programmers. . can u help me with this project of mine?

it needs a pemdas and mdas rule . but i dont know how to put it.

can u please help me with this?

i really appreciate ur help. thanks guys. .

God bless


import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
import java.util.*;

public class MDAS {

private String inputString = null;

JLabel expression = new JLabel("Expression: ");
JLabel result = new JLabel("Result: ");
JTextField expression_textf = new JTextField(20);
JTextField result_textf = new JTextField(10);


JButton calculate = new JButton(" Calculate");
JButton clear = new JButton(" Clear ");
JButton cancel = new JButton (" Cancel ");

//text functions
public JPanel text_2() {


JPanel Panel1 = new JPanel();
JPanel Panel2 = new JPanel();

Panel1.setLayout(new GridLayout(4,4));
Panel1.add(expression);
Panel1.add(expression_textf);
Panel1.add(result);
Panel1.add(result_textf);
result_textf.setEnabled(false);
result_textf.setFont(new Font("Comic Sans Ms", Font.PLAIN, 18));
Panel2.setLayout(new FlowLayout(FlowLayout.RIGHT));
Panel2.add(Panel1);

return Panel2;

}
//Button functions
public JPanel buttons_3(){

clear.addActionListener ( new ActionListener () {
public void actionPerformed (ActionEvent e) {

clear();
}
});

calculate.addActionListener ( new ActionListener () {
public void actionPerformed (ActionEvent e) {

process();
}
});
cancel.addActionListener ( new ActionListener () {
public void actionPerformed (ActionEvent e) {

process();
}
});


JPanel Panel1 = new JPanel();
JPanel Panel2 = new JPanel();
Panel1.setLayout(new GridLayout(5, 6));


Panel2.add(calculate);
Panel2.add(clear);
Panel2.add(cancel);

Panel2.setLayout(new FlowLayout(FlowLayout.RIGHT));
Panel2.add(Panel1);

return Panel2;


}

//Processing and display output
protected void process()
{
// get the input string
inputString = expression_textf.getText();

// Out the string
inputString = inputString.trim();

// Ensure there are characters to process
if (inputString.length() > 0)
// check syntax, evaluate and display results if correct
if ( checkSyntax() )
result_textf.setText( ""+ evaluate() );

}

protected boolean checkSyntax()
{
int opCount = 1; // Start with a value
boolean hasDec = false; // Does the current # have a decimal component?
int i;

// Check each character
for (i = 0; i < inputString.length(); i++)
switch(inputString.charAt(i))
{
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':

opCount = 0;
break;
case '.':
if (((opCount += 2) > 2) || hasDec)

hasDec = true;
break;
case '%':
case '/':
case '*':
if (opCount++ > 0)

hasDec = false;
break;
case '%':
case '+':
case '-':
if (opCount++ > 1)

hasDec = false;
break;
default:
return reportError(i);
}

// Make sure expression ends with a value

return true;
}

protected double evaluate()
{
// Temp token handle
String tok1, tok2;

// Create a string tokenizer object, keeping the delimiters as tokens
StringTokenizer tokens = new StringTokenizer( inputString, "+-/*", true );

// get the first token and put its value into result
if ((tok1 = tokens.nextToken()).equals("*"))
tok1 = tokens.nextToken();
else if (tok1.equals("/"))
tok1 = "-".concat(tokens.nextToken());
else if (tok1.equals("+"))
tok1 = "-".concat(tokens.nextToken());
else if (tok1.equals("-"))
tok1 = "-".concat(tokens.nextToken());
else if (tok1.equals("%"))
tok1 = "%".concat(tokens.nextToken());
double result = new Double(tok1).doubleValue();

// Evaluate the expression
while (tokens.hasMoreTokens())
{
// Get the operator token
tok1 = tokens.nextToken();

// Get the second operand token
if ((tok2 = tokens.nextToken()).equals("*"))
tok2 = tokens.nextToken();
else if (tok2.equals("/"))
tok2 = "-".concat(tokens.nextToken());
else if (tok2.equals("+"))
tok2 = "-".concat(tokens.nextToken());
else if (tok2.equals("-"))
tok2 = "-".concat(tokens.nextToken());
else if (tok2.equals("%"))
tok2 = "%".concat(tokens.nextToken());

// Evaluate the subexpression
switch (tok1.charAt(0))
{
case '+':
result += new Double(tok2).doubleValue();
break;
case '-':
result -= new Double(tok2).doubleValue();
break;
case '/':
result /= new Double(tok2).doubleValue();
break;
case '*':
result *= new Double(tok2).doubleValue();
break;
case '%':
result %= new Double(tok2).doubleValue();
break;
}
}
return result;
}
public void clear() {

expression_textf.setText("");
result_textf.setText("");

}
protected boolean reportError( int index )
{
// create a new string with the first line of output
String outputString = new String("Invalid Number\n");


// copy the output string text to the output text area
result_textf.setText( outputString );

return false;
}

public JFrame buildNewFrame() {

try{
UIManager.setLookAndFeel(
UIManager.getSystemLookAndFeelClassName());


}catch(Exception e){}

MDAS re = new MDAS();

JPanel nPanel = new JPanel();
JPanel sPanel = new JPanel();
JPanel fPanel = new JPanel();

nPanel = re.text_2 ();
sPanel = re.buttons_3 ();


fPanel.setLayout( new BorderLayout());
fPanel.add(nPanel, BorderLayout.CENTER);
fPanel.add(sPanel, BorderLayout.SOUTH);


JFrame frame = new JFrame("MDAS");

frame.setSize(50,50);
frame.getContentPane().add(fPanel);

frame.addWindowListener( new WindowAdapter() {

public void windowClosing( WindowEvent e) {

System.exit(0);
}
});

return frame;

}

}


















/// runner ///

import javax.swing.JFrame;

public class MDAS_Runner {

public static void main(String args[]){

JFrame run = new JFrame();
MDAS rece = new MDAS ();
run = rece.buildNewFrame();

run.pack();
run.setVisible(true);

}

}

[Norm]

Could define: pemdas and mdas rule
and how that relates to java programming?

[clark_sandy]

well. . i got the calculator working but its not following the mdas rule. u know wen i type 5-1*8-9 , the answer would be -12 by follwing the mdas rule. but in my calculator program, the result will be 23.

Does anyone have any suggestions? thanks for the reply. .

God bless

[Norm]

What is the mdas rule?
Does it relate to operator precedence?
Your code will have to parse the expression and do the operations in the order of precedence. There are various methods for doing that. A simple one would be to scan the expression for the highest level operation, pick up its operands, do the operation and replace the operands and operation with the results and do it again until there are no operations left to do.
It looks like your code is doing the operations from left to right.